The environmental group Our Children's Trust issued a statement Nov. 12, claiming the energy industry is threatened by the lawsuit because "nearly every oil and gas company in the world asked for permission to oppose" it.

"In an unusual step, the immense fossil fuel industry trade groups all filed pleadings in the U.S. district court for the District of Oregon seeking to join the lawsuit side by side with President Obama to protect their companies' interests," said the trust statement.

15-year old Xiuhtezcatl Tonatiuh Martinez, a member of the group, became a climate change activist at age 6 when he saw an environmental documentary. He asked his mom to find a way for him to speak at a rally.